Passengers are being advised not to travel on trains during strikes next week as it was revealed half of lines will be closed with only about a fifth of services running.
The national rail timetable from 20 June to 26 June is still being finalised but the number of services is expected to be around 4,500 compared with 20,000 normally, Network Rail said.
But disruption is also likely to hit non-strike days next week when only about 60 per cent of normal services will run.
Southeastern and TransPennine are among the rail operators urging passengers to “only travel by rail if necessary”. Northern has asked people “not to travel” on trains between Tuesday and Sunday.
The full scale of the impact of the strikes was revealed on Wednesday with Network Rail announcing there would be no passenger services serving locations such as Penzance in Cornwall, Bournemouth in Dorset, Swansea in South Wales, Holyhead in North Wales, Chester in Cheshire and Blackpool, Lancashire.
There will also be no passenger trains running north from Glasgow or Edinburgh.
Open lines include the West Coast Main Line from London to Scotland via locations such as Birmingham and Manchester.
The number of passenger services on the strike days is expected to be limited to around 4,500 compared with 20,000 normally.
Members of the Rail, Maritime and Transport union at Network Rail and 13 train operators are to strike for three days next week in similar disputes over pay, jobs and pensions.
Lines will only be open between 7.30am and 6.30pm, meaning services will start later and finish earlier than usual.
Passengers “who must travel” are urged to “plan ahead” to ensure they can complete their journeys within this window, Network Rail said.
Last services from London to Scotland will leave in the early afternoon.
Steve Montgomery, who chairs industry body the Rail Delivery Group, said: “These strikes will affect the millions of people who use the train each day, including key workers, students with exams, those who cannot work from home, holidaymakers and those attending important business and leisure events.
“Working with Network Rail, our plan is to keep as many services running as possible, but significant disruption will be inevitable and some parts of the network will not have a service, so passengers should plan their journeys carefully and check their train times.”
Mr Johnson hit out first, when being grilled over the cost-of-living crisis, rounding on Sir Keir by saying: “What would be useful in supporting the UK economy right now would be if the leader of the Labour Party ended his sphinx-like silence about the RMT strikes coming up.
Sir Keir responded: “He’s in government. He could do something to stop the strikes. But he has not lifted a finger.
“I don’t want the strikes to go ahead but he does. He wants the country to grind to a halt so he can feed off the division.”
However, the Labour leader stopped short of directly criticising the Rail, Maritime and Transport union over the strikes planned next week.
Mr Johnson accused Labour of being “on the side” of the RMT strikers, adding: “We are on the side of the travelling public.”